Why don't hair particles rendered as an object follow parent object when the parent object is falling under gravity as a rigid body?
I probably need some screenshots, but I'll give it a shot:
Blender hair physics cannot get the same physical behaviour as their visualized object. Not that the object gets inserted in the "Render" tab, not the physics tab. Hair have their own strand based physics, which are limited. Unfortunately (to my knowledge and frustration) you cannot even make the rendered object bend along the hair's path. 
If that wasn't your question, make sure you did this: 


If your using softbody, make sure they are above the hair in the modifier stack. And lastly, make sure to bake the rigidbody animation to keyframes. 

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